Improved Cleanroom Relauncher

Makes the Cleanroom Relauncher a much more seamless experience for modpack users and allows modpack creators to not have to worry about setup instructions! It will automatically download the required java version and cleanroom libraries, and configure it automatically for you!

Relaunches a Forge 1.12.2 instance with Cleanroom Loader, with a streamlined first-run experience and automatic Java setup.

Features

Automatic Java download and setup
- Configurable major version (default: 24)
- Configurable distribution (default: Adoptium)
Cross-platform and arch-aware
- Windows: x64, ARM64
- Linux: x64, aarch64
- macOS: Intel (x64), Apple Silicon (aarch64)
First-run automation
- Auto-selects the latest Cleanroom Loader release
- Progress popup: "Setting Up Necessary Libraries (Only Happens Once)" with download progress
Auto-switch Java when config javaVersion changes
Automatic download resuming and retrying

First run setup

If no Java path is configured, the relauncher downloads Java for your OS/architecture and config javaVersion.
A progress dialog shows the download status and then the archive is extracted automatically.
The latest Cleanroom Loader release is selected automatically (no manual selection needed).

Configuration

File: config/relauncher.json
Key options:
- javaVersion: desired major version (e.g., 21, 24). Changing this triggers an automatic re-download and switch.
- javaExecutablePath: set if you want to force a specific Java. If it’s not valid or mismatched with javaVersion, the relauncher will auto-download the correct one.

Cache locations

Java is cached under: <UserHome>/.cleanroom/relauncher/java/<distribution>-<version>-<os>-<arch>
- Example: ~/.cleanroom/relauncher/java/temurin-21-windows-x64
- Example: ~/.cleanroom/relauncher/java/graalvm-22-linux-x64
- Example: ~/.cleanroom/relauncher/java/graalvm-24-mac-aarch64

It offers a GUI on the client for manual configuration when the autoconfiguration fails.

Cleanroom Loader is a new loader developed from the roots of Forge Mod Loader for Minecraft 1.12.2 specifically. It boasts better performance, modern Java support, and offers better experiences for mod developers.